linux-kernel - [PATCH] regmap: Account for register length when chunking

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Message-ID: <20230516155223.2070731-1-jwylder@google.com>
Date:   Tue, 16 May 2023 10:52:23 -0500
From:   Jim Wylder <jwylder@...gle.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, Jim Wylder <jwylder@...gle.com>
Subject: [PATCH] regmap: Account for register length when chunking

Currently, when regmap_raw_write() splits the data, it uses the
max_raw_write value defined for the bus.  For any bus that includes
the target register address in the max_raw_write value, the chunked
transmission will always exceed the maximum transmission length.
To avoid this problem, subtract the length of the register from the
maximum transmission.

Signed-off-by: Jim Wylder <jwylder@...gle.com>
---
 drivers/base/regmap/regmap.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index db7851f0e3b8c..1d1496c253ca6 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -2083,14 +2083,15 @@ int _regmap_raw_write(struct regmap *map, unsigned int reg,
 	size_t chunk_count, chunk_bytes;
 	size_t chunk_regs = val_count;
 	int ret, i;
+	size_t max_data = map->max_raw_write - map->format.reg_bytes;
 
 	if (!val_count)
 		return -EINVAL;
 
 	if (map->use_single_write)
 		chunk_regs = 1;
-	else if (map->max_raw_write && val_len > map->max_raw_write)
-		chunk_regs = map->max_raw_write / val_bytes;
+	else if (map->max_raw_write && val_len > max_data)
+		chunk_regs = max_data / val_bytes;
 
 	chunk_count = val_count / chunk_regs;
 	chunk_bytes = chunk_regs * val_bytes;

base-commit: ad2fd53a7870a395b8564697bef6c329d017c6c9
-- 
2.40.1.606.ga4b1b128d6-goog